Fix test for organisations in brand selection page
Fix test for organisations in brand selection page

This test was a duplicate of that for branding
showing. This renames them both to better explain
what they do and makes the later one check for
branding styles.

This also removes the
`mock_get_letter_email_branding` param from the
first test as it wasn't being used.

alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin,alphagov/notifications-admin